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Studies on the interaction between ciprofloxacin hydrochloride and diclofenac sodium

Dina El-Sabawi
Rana Abu-Dahab
Amal G. Al Bakri
Imad I. Hamdan


Purpose: To study the interaction between ciprofloxacin hydrochloride (Cipro) and diclofenac sodium (DS) in the presence and absence of metal ions.

Methods: Complexes were prepared in the aqueous phase at different molar ratios (r) of Cipro:DS (ranged from 0.2 – 2.0). The complexes were characterized by Fourier transform-infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and high pressure liquid chromatography (HPLC). Their properties, i.e., solubility, dissolution and partition coefficient (log P), were studied along with their permeability across Caco-2 cells. Furthermore, the antimicrobial activity of Cipro and its complexes was determined using standard broth dilution method and expressed as minimum inhibitory concentration (MIC).

Results: Cipro formed an ion pair with DS. The product was confirmed to be a combination of the two drugs, DS and Cipro, but in a ratio that is dependent on the added amounts of each component (r = 1:1 or 1:2). The 1:1 product was more lipophilic than the individual components leading to a lower aqueous solubility and a higher octanol/water partition coefficient log P (6.7 vs. 0.77). The presence of DS within the dissolution medium appeared to modify the dissolution of Cipro depending on the concentration. Moreover, ternary complexes involving Cipro, DS and metal ions (iron and/or calcium) exhibited improved antimicrobial effect (MIC, 0.016 μg/ml compared to 0.258 μg/ml for Cipro). Caco-2 cell permeation data indicate that the presence of DS significantly improved the apparent permeability coefficient (Papp) of Cipro (20.6 × 10-6 cm/s) which was three times higher than that of free Cipro (p < 0.05). DS also appeared to counteract the well-known negative effect of metal ions on the bioavailability of Cipro.

Conclusion: There is a clinically relevant interaction between DS and Cipro at the absorption level as a result of ion pair formation, which might even counteract the negative effect of metals on the absorption of Cipro. These findings should aid the design of new Cipro ion pairs that provide higher bioavailability than free Cipro.

Keywords: Ciprofloxacin, Diclofenac, Interaction, Ion pair, Permeability coefficient, Bioavailability, Absorption